1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /* Copyright (c) 2020 Pengutronix, Marc Kleine-Budde <kernel@pengutronix.de>
3 * Copyright (c) 2021 Vincent Mailhol <mailhol.vincent@wanadoo.fr>
4 */
5
6 #ifndef _CAN_BITTIMING_H
7 #define _CAN_BITTIMING_H
8
9 #include <linux/netdevice.h>
10 #include <linux/can/netlink.h>
11
12 #define CAN_SYNC_SEG 1
13
14 #define CAN_BITRATE_UNSET 0
15 #define CAN_BITRATE_UNKNOWN (-1U)
16
17 #define CAN_CTRLMODE_FD_TDC_MASK \
18 (CAN_CTRLMODE_TDC_AUTO | CAN_CTRLMODE_TDC_MANUAL)
19 #define CAN_CTRLMODE_TDC_AUTO_MASK \
20 (CAN_CTRLMODE_TDC_AUTO)
21 #define CAN_CTRLMODE_TDC_MANUAL_MASK \
22 (CAN_CTRLMODE_TDC_MANUAL)
23
24 /*
25 * struct can_tdc - CAN FD Transmission Delay Compensation parameters
26 *
27 * At high bit rates, the propagation delay from the TX pin to the RX
28 * pin of the transceiver causes measurement errors: the sample point
29 * on the RX pin might occur on the previous bit.
30 *
31 * To solve this issue, ISO 11898-1 introduces in section 11.3.3
32 * "Transmitter delay compensation" a SSP (Secondary Sample Point)
33 * equal to the distance from the start of the bit time on the TX pin
34 * to the actual measurement on the RX pin.
35 *
36 * This structure contains the parameters to calculate that SSP.
37 *
38 * -+----------- one bit ----------+-- TX pin
39 * |<--- Sample Point --->|
40 *
41 * --+----------- one bit ----------+-- RX pin
42 * |<-------- TDCV -------->|
43 * |<------- TDCO ------->|
44 * |<----------- Secondary Sample Point ---------->|
45 *
46 * To increase precision, contrary to the other bittiming parameters
47 * which are measured in time quanta, the TDC parameters are measured
48 * in clock periods (also referred as "minimum time quantum" in ISO
49 * 11898-1).
50 *
51 * @tdcv: Transmitter Delay Compensation Value. The time needed for
52 * the signal to propagate, i.e. the distance, in clock periods,
53 * from the start of the bit on the TX pin to when it is received
54 * on the RX pin. @tdcv depends on the controller modes:
55 *
56 * CAN_CTRLMODE_TDC_AUTO is set: The transceiver dynamically
57 * measures @tdcv for each transmitted CAN FD frame and the
58 * value provided here should be ignored.
59 *
60 * CAN_CTRLMODE_TDC_MANUAL is set: use the fixed provided @tdcv
61 * value.
62 *
63 * N.B. CAN_CTRLMODE_TDC_AUTO and CAN_CTRLMODE_TDC_MANUAL are
64 * mutually exclusive. Only one can be set at a time. If both
65 * CAN_TDC_CTRLMODE_AUTO and CAN_TDC_CTRLMODE_MANUAL are unset,
66 * TDC is disabled and all the values of this structure should be
67 * ignored.
68 *
69 * @tdco: Transmitter Delay Compensation Offset. Offset value, in
70 * clock periods, defining the distance between the start of the
71 * bit reception on the RX pin of the transceiver and the SSP
72 * position such that SSP = @tdcv + @tdco.
73 *
74 * @tdcf: Transmitter Delay Compensation Filter window. Defines the
75 * minimum value for the SSP position in clock periods. If the
76 * SSP position is less than @tdcf, then no delay compensations
77 * occur and the normal sampling point is used instead. The
78 * feature is enabled if and only if @tdcv is set to zero
79 * (automatic mode) and @tdcf is configured to a value greater
80 * than @tdco.
81 */
82 struct can_tdc {
83 u32 tdcv;
84 u32 tdco;
85 u32 tdcf;
86 };
87
88 /*
89 * struct can_tdc_const - CAN hardware-dependent constant for
90 * Transmission Delay Compensation
91 *
92 * @tdcv_min: Transmitter Delay Compensation Value minimum value. If
93 * the controller does not support manual mode for tdcv
94 * (c.f. flag CAN_CTRLMODE_TDC_MANUAL) then this value is
95 * ignored.
96 * @tdcv_max: Transmitter Delay Compensation Value maximum value. If
97 * the controller does not support manual mode for tdcv
98 * (c.f. flag CAN_CTRLMODE_TDC_MANUAL) then this value is
99 * ignored.
100 *
101 * @tdco_min: Transmitter Delay Compensation Offset minimum value.
102 * @tdco_max: Transmitter Delay Compensation Offset maximum value.
103 * Should not be zero. If the controller does not support TDC,
104 * then the pointer to this structure should be NULL.
105 *
106 * @tdcf_min: Transmitter Delay Compensation Filter window minimum
107 * value. If @tdcf_max is zero, this value is ignored.
108 * @tdcf_max: Transmitter Delay Compensation Filter window maximum
109 * value. Should be set to zero if the controller does not
110 * support this feature.
111 */
112 struct can_tdc_const {
113 u32 tdcv_min;
114 u32 tdcv_max;
115 u32 tdco_min;
116 u32 tdco_max;
117 u32 tdcf_min;
118 u32 tdcf_max;
119 };
120
121 struct data_bittiming_params {
122 const struct can_bittiming_const *data_bittiming_const;
123 struct can_bittiming data_bittiming;
124 const struct can_tdc_const *tdc_const;
125 struct can_tdc tdc;
126 const u32 *data_bitrate_const;
127 unsigned int data_bitrate_const_cnt;
128 int (*do_set_data_bittiming)(struct net_device *dev);
129 int (*do_get_auto_tdcv)(const struct net_device *dev, u32 *tdcv);
130 };
131
132 #ifdef CONFIG_CAN_CALC_BITTIMING
133 int can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt,
134 const struct can_bittiming_const *btc, struct netlink_ext_ack *extack);
135
136 void can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const,
137 const struct can_bittiming *dbt,
138 u32 tdc_mask, u32 *ctrlmode, u32 ctrlmode_supported);
139 #else /* !CONFIG_CAN_CALC_BITTIMING */
140 static inline int
can_calc_bittiming(const struct net_device * dev,struct can_bittiming * bt,const struct can_bittiming_const * btc,struct netlink_ext_ack * extack)141 can_calc_bittiming(const struct net_device *dev, struct can_bittiming *bt,
142 const struct can_bittiming_const *btc, struct netlink_ext_ack *extack)
143 {
144 netdev_err(dev, "bit-timing calculation not available\n");
145 return -EINVAL;
146 }
147
148 static inline void
can_calc_tdco(struct can_tdc * tdc,const struct can_tdc_const * tdc_const,const struct can_bittiming * dbt,u32 tdc_mask,u32 * ctrlmode,u32 ctrlmode_supported)149 can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const,
150 const struct can_bittiming *dbt,
151 u32 tdc_mask, u32 *ctrlmode, u32 ctrlmode_supported)
152 {
153 }
154 #endif /* CONFIG_CAN_CALC_BITTIMING */
155
156 void can_sjw_set_default(struct can_bittiming *bt);
157
158 int can_sjw_check(const struct net_device *dev, const struct can_bittiming *bt,
159 const struct can_bittiming_const *btc, struct netlink_ext_ack *extack);
160
161 int can_get_bittiming(const struct net_device *dev, struct can_bittiming *bt,
162 const struct can_bittiming_const *btc,
163 const u32 *bitrate_const,
164 const unsigned int bitrate_const_cnt,
165 struct netlink_ext_ack *extack);
166
167 /*
168 * can_get_relative_tdco() - TDCO relative to the sample point
169 *
170 * struct can_tdc::tdco represents the absolute offset from TDCV. Some
171 * controllers use instead an offset relative to the Sample Point (SP)
172 * such that:
173 *
174 * SSP = TDCV + absolute TDCO
175 * = TDCV + SP + relative TDCO
176 *
177 * -+----------- one bit ----------+-- TX pin
178 * |<--- Sample Point --->|
179 *
180 * --+----------- one bit ----------+-- RX pin
181 * |<-------- TDCV -------->|
182 * |<------------------------>| absolute TDCO
183 * |<--- Sample Point --->|
184 * | |<->| relative TDCO
185 * |<------------- Secondary Sample Point ------------>|
186 */
can_get_relative_tdco(const struct data_bittiming_params * dbt_params)187 static inline s32 can_get_relative_tdco(const struct data_bittiming_params *dbt_params)
188 {
189 const struct can_bittiming *dbt = &dbt_params->data_bittiming;
190 s32 sample_point_in_tc = (CAN_SYNC_SEG + dbt->prop_seg +
191 dbt->phase_seg1) * dbt->brp;
192
193 return (s32)dbt_params->tdc.tdco - sample_point_in_tc;
194 }
195
196 /*
197 * can_bit_time() - Duration of one bit
198 *
199 * Please refer to ISO 11898-1:2015, section 11.3.1.1 "Bit time" for
200 * additional information.
201 *
202 * Return: the number of time quanta in one bit.
203 */
can_bit_time(const struct can_bittiming * bt)204 static inline unsigned int can_bit_time(const struct can_bittiming *bt)
205 {
206 return CAN_SYNC_SEG + bt->prop_seg + bt->phase_seg1 + bt->phase_seg2;
207 }
208
209 #endif /* !_CAN_BITTIMING_H */
210